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Phil Gavin avatar image
Phil Gavin asked

Starting a big pump off grid, does anyone switch in a generator first?

The planned scenario is to have 3 x 15kVA Quattros, in 3 ph totally off-grid.

I have an 11kW pump that I want to use for irrigation. It has a star/delta starter already to limit the starting current. Measurements aside, I don't think the inverters will handle it.

A soft starter won't cut it on an inverter.

I am looking at a VFD, but I'm concerned about the harmonics as the pump will constitute the majority of the load. There are filters etc I know but it all adds up.

So I am considering a (smaller, maybe 7 kVAish) 3-ph generator to feed the Quattro's on the AC in just to supply the extra oomph to start the pump and then switching it out and letting the solar take over.

The generator is also there if needs be for other uses, but the VFD is a dedicated use.

If anyone has gone down this route I'd like to hear if a generator is a feasible option.

starting generator
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1 Answer
Alexandra avatar image
Alexandra answered ·

@Phil Gavin

If you are concerned the 3phase 15kva system wont start it a little 7kv generator wont help at all. I am assuming the 11kwh pump is a three phase pump?

Is your battery wiring on point?

We can start 2 x 7kw irrigation pumps simultaneously on a 3phase 15kva setup, it does not even blink. But have a fairly beefy battery and wiring setup. There are no vfds or even a star delta start.

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Phil Gavin avatar image Phil Gavin commented ·
An interesting experience, are you totally off-grid with no AC aiding your Quattro's and are these direct-on-line motors connected in delta?
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Alexandra avatar image Alexandra ♦ Phil Gavin commented ·
Yes totally off grid.

Have started the load with no solar assistance at night as well. Again, no costs cut in DC cabling and battery bank sizing.

They are DOL.


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Phil Gavin avatar image Phil Gavin Alexandra ♦ commented ·

This gives me hope, thanks.

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